This invention relates to an articulated splint for the knee joint, i.e., a splint intended to function in conjunction with a cast or an orthotic sleeve constructed from other material such as plastic, felt, elastic and the like without blocking the knee joint. Such splints are used for treating fractures, re-education therapy of an arthrolysis, orthopedic treatment of limbs after surgical correction, early re-education therapy of ligamentous lesions and to provide restraining articulated orthoses for traumatic knee lesions and other knee injuries of the type which occur to athletes.
This type of splint generally is composed of two symmetrical side portions each of which is made up of two uprights, an upper femoral upright and a lower tibial upright, connected to one another by a rod. Each of the uprights is intended to be fastened, with its counterpart of the other side portion, against one of the lateral faces of the corresponding part of a leg by a single cast or the like covering both side portions of the splint whose central part covering the knee is then cut or eliminated.
Two general types of splints are now distinguished, these simply being monoaxial splints and polycentric splints.
Since the knee joint is a complex joint whose axis of rotation moves over a curve as a function of a well determined law, neither of the two types of splints mentioned above are satisfactory. By the very fact that the first is a simple articulation, its tibial element can only constitute a hindrance to the movements of the tibia, the axes of rotation of the splint and knee being able to coincide, at best, only in a particular determined angular position of the tibial in relation to the femur.
Of the polycentric splints, there are those each of whose uprights is coupled to the other by a rod and train of three gears of which two are keyed on connecting pins of the rod to each of the uprights and whose third gear, mounted free in rotation on a pin carried by the rod, meshes with each of the other two and connects them in rotation. In this splint, the connecting pin of the lower or tibial upright, consequently moves over an arc of a circle, which, although representing an advance in comparison with the monoaxial type splint, does not faithful reproduce the motion of the knee joint and as a result produces mechanical constraints contrary to the normal physiology of the knee.
There is further known a polycentric splint without a connecting pin and in which the two uprights of each its two side portions are connected to one another by a central part of high-density polyethylene, this type of splint functions by virture of deformation and is either too rigid, constituting an impedement, or too flexible, to accomplish its aim.